In general, not all of the CBD you consume will directly affect your body: only a certain percentage will be able to enter your systemic circulation and produce its active effects. This percentage is referred to in science as “bioavailability,” and it strongly depends on the manner in which CBD is introduced to your system. For example, the oral bioavailability of CBD is roughly 15 percent. That means for every 100 milligrams of CBD that you eat, only 15 milligrams will actually reach your bloodstream.
There are two main reasons why this happens. First, CBD is hydrophobic, meaning that it is not very water-soluble. In the same way that oil does not like to mix with vinegar, CBD does not like to stay in your bloodstream. Instead, it rapidly diffuses out of your blood and accumulates into your fatty tissues. Unfortunately, this significantly reduces the amount of bioactive CBD that can enter your systemic circulation, allowing for less CBD to be carried to its active sites in your body and thus lowering its overall bioavailability.
Second, when an organic compound like CBD enters your gut, it has to pass through the liver before it enters your circulation. During this transition, the liver will actively reduce the amount of CBD, either through absorption or through chemical breakdown by liver enzymes. This phenomenon is called the “first-pass effect,” where passing through the liver reduces the concentration of bioactive compounds.
There are a few different ways to offset these losses of CBD. For one, you can reduce the amount of CBD that dissolves out of your bloodstream by putting the CBD into a form that is more hydrophilic, or water-soluble. However, this can only be achieved by complicated chemical means, such as through the use of cyclodextrins or liposomes. A more practical solution is to bypass the first-pass effect of oral administration entirely by utilizing vaporization.
During vaporization, CBD enters your lungs and diffuses directly into your bloodstream rather than passing through your gut and liver. This avoids the first-pass effect altogether, allowing nearly four times as much CBD to enter your circulation for a maximum bioavailability of roughly 50 to 60 percent. Essentially, this means you can achieve the same beneficial effects with a much smaller amount of CBD.